Liquid metal-based dual-network magnetic hydrogel as well as preparation method and application thereof

Abstract

The invention relates to liquid metal-based dual-network magnetic hydrogel as well as a preparation method and application thereof. The hydrogel comprises dual-network hydrogel and magnetic Fe3O4 nanoparticles loaded in a network structure of the dual-network hydrogel, the double-network hydrogel comprises a first network structure and a second network structure, wherein the first network structure is a network structure formed by polymerizing a liquid metal coated sodium alginate chain, and the second network structure is a polyacrylamide network structure formed by polymerizing an acrylamide monomer; the mass ratio of the liquid metal to the magnetic Fe3O4 nanoparticles is (0.5-2): (0.5-1.0). Compared with the prior art, the composite hydrogel not only can effectively shield electromagnetic radiation, but also has good intelligent magnetic responsiveness, and the application prospect of the composite hydrogel in the fields of intelligent materials, sensors, electromagnetic shielding and the like is widened.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave shielding materials technology, and in particular relates to a liquid metal-based dual-network magnetic hydrogel, its preparation method and application. Background Technology

[0002] With the continuous development of intelligent electronic devices, especially their widespread application in wearable electronic devices, flexible displays, and self-powered systems, higher requirements are being placed on material performance. Multifunctional integrated electromagnetic shielding materials have gradually become a research hotspot. They not only have significant application potential in intelligent equipment, sensors, and medical devices, but also have significant advantages in improving the functionality of materials.

[0003] In recent years, composite materials based on liquid metals and polymer hydrogels have gradually attracted researchers' attention. Among them, sodium alginate-polyacrylamide (SA-PAM) composite hydrogels, as a novel flexible hydrogel material, possess excellent biocompatibility, environmental friendliness, and tunability, and have been widely used in biomedicine, sensors, smart electronics, and energy storage. Liquid metals, due to their high conductivity, fluidity, and tunability, have potential applications in multiple fields, especially in flexible electronic devices, wearable technologies, and electromagnetic shielding materials, demonstrating significant advantages. The application of liquid metals in flexible materials can not only provide efficient electron conduction channels but also achieve self-healing and reconfigurable functions.

[0004] In recent years, composite materials of liquid metal particles and polymers have been widely used in strain sensing, ultra-flexible circuits, and sensors. For example, CN114702690A discloses a gallium / sodium alginate / polyacrylamide composite hydrogel material, its preparation method, and its applications. A high-toughness conductive hydrogel is formed through ultrasonic treatment and cross-linking reaction. Utilizing the liquid properties of gallium and the cross-linking effect of sodium alginate, combined with the network structure of polyacrylamide, the elasticity and conductivity of the hydrogel are improved, resulting in high skin adhesion and adaptability to complex deformations. However, this composite hydrogel material still cannot effectively shield electromagnetic radiation, nor can its morphology or structure be adjusted under the influence of an external magnetic field, and it does not possess intelligent response characteristics.

[0005] Therefore, there is an urgent need to develop a novel flexible hydrogel composite material with electromagnetic shielding properties and magnetic responsiveness to provide new solutions for the development of intelligent equipment and sensors. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing flexible hydrogel composite materials in achieving effective electromagnetic shielding and magnetic response control, and to provide a liquid metal-based dual-network magnetic hydrogel, its preparation method, and its application.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention first provides a liquid metal-based dual-network magnetic hydrogel, which includes a dual-network hydrogel and magnetic Fe3O4 nanoparticles loaded in the network structure of the dual-network hydrogel.

[0009] The dual-network hydrogel includes a first network structure and a second network structure;

[0010] The dual-network hydrogel includes a first network structure and a second network structure; wherein, the first network structure is a network structure formed by polymerizing sodium alginate chains coated with liquid metal, and the second network structure is a polyacrylamide network structure formed by polymerizing acrylamide monomers.

[0011] The mass ratio of the liquid metal to the magnetic Fe3O4 nanoparticles is (0.5-2):(0.5-1).

[0012] Furthermore, the dual-network hydrogel has a porous sponge-like structure with a pore size of 20-50 μm.

[0013] Furthermore, the sodium alginate coating of liquid metal forms micron-sized particles with a diameter of 1-3 μm.

[0014] Furthermore, the magnetic Fe3O4 nanoparticles have a particle size of 50-200 nm.

[0015] Furthermore, the liquid metal is gallium, rubidium, cesium, or an alloy containing the above metals.

[0016] Furthermore, the liquid metal-based dual-network magnetic hydrogel exhibits a tensile strength of 50–290 kPa, a Young's modulus of 60–250 kPa, and a toughness of 3.5–12 MJ / m. -3 .

[0017] Furthermore, the mass content of the magnetic Fe3O4 nanoparticles in the liquid metal-based dual-network magnetic hydrogel is 12.5-40.0 wt.%.

[0018] This invention also provides a method for preparing a liquid metal-based dual-network magnetic hydrogel, the method comprising the following steps:

[0019] S1. Preparation of liquid metal dispersion: Disperse liquid metal in water and use a cell disruptor for ultrasonic-assisted dispersion to obtain a micron-sized liquid metal dispersion;

[0020] S2. Preparation of sodium alginate-coated liquid metal micron particles: The liquid metal aqueous dispersion obtained in S1 is added to the sodium alginate aqueous solution, and then dispersed again by ultrasonic-assisted dispersion using a cell disruptor to obtain a mixed solution containing sodium alginate-coated liquid metal micron particles.

[0021] S3. Preparation of dual-network hydrogel precursor solution: Add acrylamide monomer, crosslinking agent and initiator to the mixed solution obtained in S2 to obtain dual-network hydrogel precursor solution;

[0022] S4. Preparation of liquid metal-based dual-network magnetic hydrogel: Magnetic Fe3O4 nanoparticles are added to the dual-network hydrogel precursor solution obtained in S3 in a certain proportion and stirred evenly. The liquid metal-based dual-network magnetic hydrogel is obtained by UV-initiated cross-linking polymerization.

[0023] Furthermore, in steps S1 and S2, the cell disruptor is set to a power of 700-900W, a frequency of 30-50kHz, and an ultrasound time of 5-10min.

[0024] Further, in step S2, the mass ratio of the liquid metal to sodium alginate is (0.5-2):0.2.

[0025] Further, in step S2, the mass concentration of sodium alginate in the sodium alginate aqueous solution is 0.03-0.05 g / mL.

[0026] Further, in step S3, the mass ratio of sodium alginate (SA), acrylamide monomer, crosslinking agent and initiator is 0.2:(1-3):(0.005-0.008):(0.01-0.02).

[0027] Furthermore, the crosslinking agent is N,N′-methylenebisacrylamide (MBA).

[0028] Furthermore, the initiator is ammonium persulfate (APS).

[0029] This invention also proposes an application of a liquid metal-based dual-network magnetic hydrogel, which serves as a flexible, multifunctional electromagnetic shielding material, possessing both electromagnetic shielding performance and magnetic response modulation performance.

[0030] Furthermore, the electromagnetic shielding mechanism of the liquid metal-based dual-network magnetic hydrogel is dominated by absorption loss.

[0031] Furthermore, the liquid metal-based dual-network magnetic hydrogel exhibits periodic unidirectional oscillations in resistance change under a 1Hz magnetic field transformation, with a peak amplitude of 6-7%.

[0032] Furthermore, the liquid metal-based dual-network magnetic hydrogel exhibits periodic bidirectional oscillations in resistance change under a 4Hz magnetic field transformation, with a peak amplitude of -2% to 5%.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) This invention introduces liquid metal and magnetic Fe3O4 nanoparticles into sodium alginate-polyacrylamide composite hydrogel, and innovatively designs a novel flexible hydrogel composite material with excellent electromagnetic shielding performance and magnetic driving performance. It was unexpectedly discovered that this composite hydrogel can not only effectively shield electromagnetic radiation, but also adjust its morphology or structure under the action of different external magnetic fields, and has good intelligent responsiveness, which broadens its application prospects in the fields of smart materials, sensors and electromagnetic shielding.

[0035] (2) In the liquid metal-based dual-network magnetic hydrogel of the present invention, the liquid metal can provide an efficient electrical conduction path, while the magnetic Fe3O4 nanoparticles can endow the composite material with good magnetic responsiveness. The combination of sodium alginate and polyacrylamide not only provides mechanical support and enhances the mechanical strength of the hydrogel, but also maintains its flexibility and controllability in the water environment, thus making it promising for a variety of practical applications.

[0036] (3) This invention utilizes the SA@LM solution and iron oxide nano-dispersion coated with sodium alginate and liquid metal micron particles obtained by cell disruption aided by ultrasound, combined with template method and ion-induced microgelization process, to prepare a multifunctional double-network liquid metal magnetic composite hydrogel by chemical cross-linking of acrylamide molecular chains and physical cross-linking of hydrogen bonding between sodium alginate. The preparation method is simple and can be prepared on a large scale.

[0037] (4) The liquid metal-based dual-network magnetic hydrogel of the present invention has a shielding mechanism dominated by absorption loss, which reduces secondary electromagnetic interference and is suitable for flexible electronics, aerospace and communications fields. The excellent electromagnetic shielding performance of the liquid metal-based dual-network magnetic hydrogel of the present invention is achieved through the synergistic driving of the conduction loss of liquid metal and the magnetic loss of Fe3O4 nanoparticles. In addition, the low-frequency response characteristics of the liquid metal-based dual-network magnetic hydrogel can be used in biomedical sensors, while the rapid fluctuation characteristics of the high-frequency response can be used in electromagnetic shielding or high-frequency communication equipment, greatly expanding its application scenarios. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating the preparation process of the liquid metal-based dual-network magnetic hydrogel of the present invention.

[0039] Figure 2These are SEM images of embodiments 1-4 of the present invention.

[0040] Figure 3 This is a comparison diagram of the mechanical properties of Embodiment 4 and Comparative Example 1 of the present invention.

[0041] Figure 4 The diagram shows the electromagnetic shielding performance of Examples 1-4 and Comparative Examples 1-2 of the present invention.

[0042] Figure 5 The magnetic field induced sensing images of the liquid metal-based dual-network magnetic hydrogel of Embodiment 4 of the present invention under low-frequency magnetic field (a) and high-frequency magnetic field (b) frequencies. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0044] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0045] The first aspect of the present invention provides a liquid metal-based dual-network magnetic hydrogel, which includes a dual-network hydrogel and magnetic Fe3O4 nanoparticles loaded in the network structure of the dual-network hydrogel.

[0046] The dual-network hydrogel includes a first network structure and a second network structure; wherein, the first network structure is a network structure formed by polymerizing sodium alginate chains coated with liquid metal, and the second network structure is a polyacrylamide network structure formed by polymerizing acrylamide monomers.

[0047] The mass ratio of the liquid metal to the magnetic Fe3O4 nanoparticles is (0.5-2):(0.5-1).

[0048] In the dual-network hydrogel structure of this invention, the first network structure is formed by the polymerization of sodium alginate chains, mainly composed of hydrogen bond interactions, which helps to improve the mechanical strength and elasticity of the material. The second network structure is a network formed by polyacrylamide chains polymerized from acrylamide monomers. This is mainly a chemically cross-linked network and is the main source of the hydrogel's mechanical strength. The dual-network cross-linking of sodium alginate and polyacrylamide provides excellent mechanical stability to this framework.

[0049] In some specific embodiments, the dual-network hydrogel has a porous sponge-like structure with a pore size of 20-50 μm. The three-dimensional interconnected and uniformly sized pore network provides an ideal framework and distribution site for the uniform dispersion of sodium alginate-coated liquid metal micron particles and magnetic Fe3O4 nanoparticles.

[0050] In some specific embodiments, the sodium alginate coating liquid metal forms micron-sized particles with a particle size of 1-3 μm.

[0051] In some specific embodiments, the magnetic Fe3O4 nanoparticles have a particle size of 50-200 nm. Introducing Fe3O4 particles into the composite material can significantly enhance the material's magnetic response, enabling it to exhibit controllable magnetic drive characteristics under the influence of an external magnetic field. Furthermore, these magnetic particles can further improve the electromagnetic shielding performance of the composite material by adjusting their dispersion and loading.

[0052] In some specific embodiments, the liquid metal is gallium, rubidium, cesium, or an alloy containing the above metals, preferably a gallium-indium alloy. Gallium-indium alloy (EGaIn) exhibits excellent fluidity and high surface tension (624 × 10⁻⁶). - 3 N·m -1 (Approximately nine times the volume of water). These "fluid cores," which are micron-sized liquid metals subjected to ultrasound, theoretically possess infinite stretchability. This is because as long as the interface can withstand continuous external pressure and the matrix can deform with the external load, these liquid metals can continue to deform.

[0053] In some specific embodiments, the liquid metal-based dual-network magnetic hydrogel has a tensile strength of 50–290 kPa, a Young's modulus of 60–250 kPa, and a toughness of 3.5–12 MJ / m. -3 It has excellent mechanical properties.

[0054] In some specific embodiments, the magnetic Fe3O4 nanoparticles in the liquid metal-based dual-network magnetic hydrogel have a mass content of 12.5-40.0 wt.%.

[0055] A second aspect of this invention provides a method for preparing a liquid metal-based dual-network magnetic hydrogel, with reference to... Figure 1 The preparation method includes the following steps:

[0056] S1. Preparation of liquid metal dispersion: Disperse liquid metal in water and use a cell disruptor for ultrasonic-assisted dispersion to obtain a micron-sized liquid metal dispersion;

[0057] S2. Preparation of sodium alginate-coated liquid metal micron particles: The liquid metal aqueous dispersion obtained in S1 is added to the sodium alginate aqueous solution, and then dispersed again by ultrasonic-assisted dispersion using a cell disruptor to obtain a mixed solution containing sodium alginate-coated liquid metal micron particles.

[0058] S3. Preparation of dual-network hydrogel precursor solution: Add acrylamide monomer, crosslinking agent and initiator to the mixed solution obtained in S2 to obtain dual-network hydrogel precursor solution;

[0059] S4. Preparation of liquid metal-based dual-network magnetic hydrogel: Magnetic Fe3O4 nanoparticles are added to the dual-network hydrogel precursor solution obtained in S3 in a certain proportion and stirred evenly. The liquid metal-based dual-network magnetic hydrogel is obtained by UV-initiated cross-linking polymerization.

[0060] In some specific embodiments, in steps S1 and S2, the cell disruptor is set to a power of 700-900W, a frequency of 30-50kHz, and an ultrasonication time of 5-10 minutes. The ultrasonication time can be extended accordingly with the increase of the amount of liquid metal added to obtain more dispersed liquid metal particles.

[0061] In some specific embodiments, in step S2, the mass ratio of the liquid metal to sodium alginate is (0.5-2):0.2.

[0062] In some specific embodiments, in step S2, the mass concentration of sodium alginate in the sodium alginate aqueous solution is 30-50 wt%, preferably 40 wt%.

[0063] In some specific embodiments, in step S3, the mass ratio of sodium alginate, acrylamide monomer, crosslinking agent and initiator is 0.2:(1-3):(0.005-0.008):(0.01-0.02).

[0064] In some more specific embodiments, the crosslinking agent is N,N′-methylenebisacrylamide (MBA).

[0065] In some more specific embodiments, the initiator is ammonium persulfate (APS).

[0066] The third aspect of this invention provides an application of a liquid metal-based dual-network magnetic hydrogel, which serves as a flexible, multifunctional electromagnetic shielding material, possessing both electromagnetic shielding performance and magnetic response modulation performance.

[0067] In some specific embodiments, the electromagnetic shielding mechanism of the liquid metal-based dual-network magnetic hydrogel is dominated by absorption.

[0068] In some specific embodiments, the liquid metal-based dual-network magnetic hydrogel exhibits periodic unidirectional oscillations in resistance change under a 1Hz magnetic field transformation, with a peak amplitude of 6-7%.

[0069] In some specific embodiments, the liquid metal-based dual-network magnetic hydrogel exhibits periodic bidirectional oscillations in resistance change under a 4Hz magnetic field transformation, with a peak amplitude of -2% to 5%.

[0070] Each of the above embodiments can be implemented individually, or in any combination of two or more. The following detailed description of specific examples will further illustrate these embodiments.

[0071] Example 1:

[0072] This embodiment provides a liquid metal-based dual-network magnetic hydrogel, specifically PSL. 0.5 F 1.0 Composite magnetic hydrogel shielding material. The preparation method is as follows:

[0073] (1) Weigh 0.5g of liquid metal (LM, gallium indium alloy) and add it to 5mL of deionized water. Shake by hand for 30s to initially disperse the blocky liquid metal into small particles in the water.

[0074] (2) Centrifuge tubes initially dispersed into small particles were placed in an ice-water bath and a cell disruptor was used with the following settings: power 800W, frequency 41.65kHz, pulse mode (sonication for 5 seconds, interval for 3 seconds), time 5 minutes. After sonication in the cell disruptor, a micron-sized liquid metal aqueous dispersion was obtained.

[0075] (3) Take 2.4g of sodium alginate (SA, molecular weight 198.11). n Add the sodium alginate (purchased from Sinopharm Chemical Reagent Co., Ltd.) to 60 mL of deionized water, adjust the magnetic stirrer to 500 rpm, and stir for 12 hours until the sodium alginate is completely dissolved to obtain an aqueous solution of sodium alginate for later use.

[0076] (4) Add the 2.0g liquid metal aqueous dispersion prepared above to a 25mL beaker containing 5mL sodium alginate aqueous solution and stir until homogeneous.

[0077] (5) Place the well-stirred beaker in an ice-water bath, and use a cell disruptor with the following program set: power 800W, frequency 41.65kHz, pulse mode (sonication for 5s, interval for 3s), time 5min, to obtain SA@LM dispersion.

[0078] (6) Weigh 2g of acrylamide (AM) monomer, 0.0065g of N,N′-methylenebisacrylamide (MBA) and 0.015g of ammonium persulfate (APS), add them to a 25mL beaker containing the above SA@LM dispersion, and stir on a magnetic stirrer until completely dissolved.

[0079] (7) Subsequently, 2 mL of a 50 wt% nano-ferric oxide dispersion (purchased from Shanghai Maclean Biochemical Technology Co., Ltd., 99.99%) was added to the above mixture and stirred until homogeneous. Finally, the mixture was quickly poured into a rectangular silicone mold, and the mold was placed under a UV lamp for 5 min to allow the mixture to polymerize and obtain a double-network composite magnetic hydrogel PSL. 0.5 F 1.0 .

[0080] Example 2:

[0081] This embodiment provides a liquid metal-based dual-network magnetic hydrogel, specifically PSL. 1.0 F 1.0 Composite magnetic hydrogel shielding material. The preparation method is as follows:

[0082] (1) Weigh 1.0g of liquid metal (LM) and add it to 5mL of deionized water. Shake by hand for 30s to initially disperse the blocky liquid metal into small particles in the water.

[0083] (2) Centrifuge tubes initially dispersed into small particles were placed in an ice-water bath and a cell disruptor was used with the following settings: power 800W, frequency 41.65kHz, pulse mode (sonication for 5 seconds, interval for 3 seconds), time 7 minutes. After sonication in the cell disruptor, a micron-sized liquid metal aqueous dispersion was obtained.

[0084] (3) Same as step 3 in Example 1.

[0085] (4) Same as step 4 in Example 1.

[0086] (5) Place the well-stirred beaker in an ice-water bath and use a cell disruptor with the following settings: power 800W, frequency 41.65kHz, pulse mode (sonication for 5s, interval for 3s), time 7min, to obtain SA@LM dispersion.

[0087] (6) Same as step 6 in Example 1.

[0088] (7) Same as step 7 in Example 1.

[0089] Example 3:

[0090] This embodiment provides a liquid metal-based dual-network magnetic hydrogel, specifically PSL. 1.5 F 1.0 Composite magnetic hydrogel shielding material. The preparation method is as follows:

[0091] (1) Weigh 1.5g of liquid metal (LM) and add it to 5mL of deionized water. Shake by hand for 30s to initially disperse the blocky liquid metal into small particles in the water.

[0092] (2) Same as step 2 in Example 2.

[0093] (3) Same as step 3 in Example 2.

[0094] (4) Same as step 4 in Example 2.

[0095] (5) Same as step 5 in Example 2.

[0096] (6) Same as step 6 in Example 2.

[0097] (7) Same as step 7 in Example 2.

[0098] Example 4:

[0099] This embodiment provides a liquid metal-based dual-network magnetic hydrogel, specifically PSL. 2.0 F 1.0 Composite magnetic hydrogel shielding material. The preparation method is as follows:

[0100] (1) Weigh 1.5g of liquid metal (LM) and add it to 5mL of deionized water. Shake by hand for 30s to initially disperse the blocky liquid metal into small particles in the water.

[0101] (2) Same as step 2 in Example 2.

[0102] (3) Same as step 3 in Example 2.

[0103] (4) Same as step 4 in Example 2.

[0104] (5) Same as step 5 in Example 2.

[0105] (6) Same as step 6 in Example 2.

[0106] (7) Same as step 7 in Example 2.

[0107] Comparative Example 1:

[0108] This comparative example provides a dual-network hydrogel without the addition of liquid metal and magnetic Fe3O4 nanoparticles. Its preparation method is as follows:

[0109] Weigh 2g of acrylamide monomer, 0.0065g of N,N′-methylenebisacrylamide (MBA) and 0.015g of ammonium persulfate, add them to a 25mL beaker containing 10mL of sodium alginate solution (0.04g / mL), and stir on a magnetic stirrer until completely dissolved.

[0110] The mixed solution was quickly poured into a rectangular silicone mold, and the silicone mold was placed under a UV lamp for 5 minutes to allow the mixed solution to polymerize and obtain a double-network hydrogel PS.

[0111] Comparative Example 2:

[0112] This comparative example provides a liquid metal-based dual-network hydrogel without the addition of magnetic Fe3O4 nanoparticles. Its preparation method is as follows:

[0113] (1) Same as step 1 in Example 4, the amount of liquid metal added is 2.0g.

[0114] (2) Same as step 2 in Example 4.

[0115] (3) Same as step 3 in Example 4.

[0116] (4) Same as step 4 in Example 4.

[0117] (5) Same as step 5 in Example 4.

[0118] (6) Same as step 6 in Example 4.

[0119] (7) Quickly pour the mixed solution into a rectangular silicone mold, place the silicone mold under a UV lamp for 5 minutes to allow the mixed solution to polymerize and obtain a double-network composite hydrogel PSL. 2.0 .

[0120] The present invention applies the following tests to the above embodiments and comparative examples:

[0121] (1) Morphological characterization: The morphology of the samples was observed using a scanning electron microscope (SEM).

[0122] (2) Mechanical property testing: Tensile properties of the composite hydrogel and film were tested using a universal testing machine. Hydrogel samples with a thickness of 1 mm and a width of 4 mm were cut into standard dumbbell-shaped strips using a custom cutter. After clamping, tensile tests were performed. The testing machine was set to run at a speed of 20 mm / min and automatically stopped after sample fracture to conduct tensile and cyclic tensile tests, obtaining the stress-strain curves of the materials. The main focus was on the elongation at break and tensile strength during the tensile process, as well as the stability and variation patterns during the cyclic tensile tests.

[0123] (3) Electromagnetic shielding performance test: Electromagnetic parameters were measured and converted into electromagnetic shielding performance using the waveguide method with the Siyi 53672B-S vector network analyzer in the frequency range of 8.2-12.4GHz.

[0124] Test sample preparation: The product is coated with a layer of different thicknesses on paper and cut into specific sizes (X-band: 3cm*2cm) for electromagnetic shielding testing.

[0125] (4) Magnetic field response performance test: The PSL prepared in Example 4 was used for the test. 2.0 F 1.0 Taking composite magnetic hydrogel shielding materials as an example, the test content is mainly based on the data of resistance under magnetic field changes, in order to determine the sensing signal characteristics of resistance change under the influence of magnetic fields of different frequencies.

[0126] like Figure 2 As shown, the liquid metal-based dual-network magnetic hydrogels prepared in Examples 1-4 all exhibit a highly porous, sponge-like structure, presenting a three-dimensional interconnected pore network with relatively uniform pore size, ranging from 50 to 150 μm in diameter. The pore walls are thin and smooth, forming a continuous framework, giving the hydrogel a lightweight and open structural characteristic. With the increase of liquid metal content, an increase in small particles or clusters embedded in or on the pore walls can be seen in the images. Tiny protrusions and depressions exist on the pore wall surface, caused by local enrichment of liquid metal or embedding of Fe3O4 nanoparticles. These particles are relatively uniformly distributed, and partially exposed particles lead to rough areas on the pore wall surface.

[0127] like Figure 3 As shown, compared to the original PS hydrogel of Comparative Example 1 (3a), the elongation of Example 4 (3b) increased from 571% to a maximum of 774%. The mechanism by which the high LM content leads to the change in mechanical properties may be related to the densification of the network structure. At an LM content of 2.0 g, the density of liquid metal particles in the matrix further increases, which may form more crosslinking points or filler effects, significantly limiting the sliding and stretching ability of the polymer chains. This high crosslinking density greatly increases the network rigidity (Young's modulus increases to 250 kPa), and also limits the deformation ability of the material under high stress, ultimately resulting in brittle fracture.

[0128] like Figure 4 As shown in the figure, the curves illustrate the characteristics of the total shielding effectiveness (SET), absorption shielding effectiveness (SEA), and reflection shielding effectiveness (SER) of the liquid metal-based dual-network magnetic hydrogels prepared in Examples 1-4 and Comparative Examples 1-2 as a function of frequency.

[0129] Specifically, such as Figure 4 As shown in a, the PSL of Example 10.5 F 1.0 The SET is approximately 40dB at 8.2GHz, increasing to 55dB at 12.4GHz; the SEA is approximately 38dB at 8.2GHz, increasing to 52dB at 12.4GHz; and the SER is approximately 2dB at 8.2GHz, decreasing to 1.5dB at 12.4GHz.

[0130] like Figure 4 As shown in b, the PSL of Example 2 1.0 F 1.0 The SEA is approximately 40 dB at 8.2 GHz, increasing to 56 dB at 12.4 GHz; the SER is approximately 4 dB at 8.2 GHz, decreasing to 2 dB at 12.4 GHz.

[0131] like Figure 4 As shown in c, the PSL of Example 3 1.5 F 1.0 The SET is approximately 50dB at 8.2GHz, increasing to 60dB at 12.4GHz; the SEA is approximately 45dB at 8.2GHz, increasing to 55dB at 12.4GHz; and the SER remains stable at 5dB in the 8.2-12.4GHz range.

[0132] like Figure 4 As shown in d, the PSL of Example 4 2.0 F 1.0 The SEA (Self-Amplitude Emission) is approximately 44 dB at 8.2 GHz, increasing to 61 dB at 12.4 GHz; the SER (Self-Amplitude Emission) is approximately 5 dB at 8.2 GHz, decreasing to 1 dB at 12.4 GHz. The SET (Self-Amplitude Emission) of the sample in Example 4 far exceeds 60 dB at 12.4 GHz, and even far exceeds the 20 dB shielding threshold in practical applications, thus attenuating most electromagnetic waves.

[0133] like Figure 4 As shown in e, the SER of the PS sample in Comparative Example 1 was 5 dB, the SEA was 14.6 dB, and the SET was 19.6 dB.

[0134] like Figure 4 As shown in f, the PSL of Comparative Example 2 2.0 The SER was 4dB, the SEA increased to 22.5dB, and the SET was 26.5dB.

[0135] In Comparative Example 1, the EMI shielding performance of the pure PS hydrogel is attributed to its hierarchical porous structure, which significantly increases the internal surface area, allowing electromagnetic waves to undergo multiple reflections within the material and effectively dissipating the energy of the incident electromagnetic waves. However, the total shielding effectiveness (SET) of only 19.6 dB is insufficient to achieve a good electromagnetic shielding effect. The reinforcing effect of liquid metal is mainly reflected in the following aspects: The high conductivity of liquid metal significantly improves the overall conductivity of the hydrogel. Especially at a content of 2.0 g, a denser conductive network is formed, promoting multiple reflections and absorptions of electromagnetic waves within the material, thereby greatly improving SEA; Liquid metal optimizes the microstructure of the hydrogel. Due to the encapsulation of liquid metal by sodium alginate chains, the liquid metal is uniformly dispersed in the hydrogel network along with SA. Furthermore, because the liquid metal is embedded in the network, it enhances the entire network, making it more suitable for electromagnetic wave dissipation and improving dielectric loss.

[0136] The results above show that SET and SEA significantly improve in the X-band with increasing liquid metal content. This is because the increased LM content enhances the conductivity of the hydrogel, forming a stronger conductive network and improving conduction loss, thus significantly increasing SEA. SER also increases from 1.5-2 dB to 5-6 dB, but remains far lower than SEA, indicating that absorption is the primary shielding mechanism in the liquid metal-based dual-network magnetic hydrogel of this invention.

[0137] Furthermore, the SET and SEA of all liquid metal-based dual-network magnetic hydrogel samples increased with increasing frequency (from 8.2 GHz to 12.4 GHz). This is because the wavelength of electromagnetic waves shortens at high frequencies, enhancing the interaction with the LM conductive network and Fe3O4 nanoparticles, leading to increased dielectric and magnetic losses. (PSL prepared in Example 4) 2.0 F 1.0 (LM content is 2.0g) The SET increase is the largest (about 15-20dB) under the above frequency changes, indicating that it is more sensitive to frequency changes.

[0138] EMI shielding effectiveness consists of reflection (SER), absorption (SEA), and multiple internal reflections. Reflection (SER) ranges from 1.5 to 6 dB, increasing slightly with LM content, but remains generally low, contributing little to SET, indicating that the surface impedance is close to the free-space impedance (377 Ω). Absorption (SEA), accounting for 70-90% of SET, dominates the shielding mechanism. This absorption-dominated shielding mechanism (SEA is much larger than SER) reduces secondary interference, making it suitable for flexible electronics, aerospace, and communications. The liquid metal-based dual-network magnetic hydrogel of this invention achieves excellent electromagnetic wave shielding effectiveness through the combined driving force of the liquid metal's conduction loss and the Fe3O4 nanoparticles' magnetic loss. The synergistic effect of the liquid metal and Fe3O4 nanoparticles significantly enhances the shielding effectiveness, with LM improving conductivity and Fe3O4 nanoparticles enhancing magnetic loss.

[0139] This invention, which uses Fe3O4 to prepare hydrogels, differs from existing MXene methods in that it introduces magnetic materials. The study investigates the composition and structure of the conductive network within the liquid metal-based composite hydrogel and the mechanism by which magnetic materials affect the hydrogel's electromagnetic shielding performance. Unexpectedly, the addition of Fe3O4 nanoparticles significantly increased the magnetic loss of the PSLF. The synergistic effect of the magnetic particles and liquid metal microdroplets achieves excellent EMI shielding performance while maintaining an absorption coefficient A above 0.4, verifying its superior electromagnetic wave loss characteristics. By constructing a magnetic sensor, the effect of the PSLF magnetic hydrogel's resistance change under varying magnetic fields was verified.

[0140] like Figure 5 As shown, the microstructure of the liquid metal-based dual-network magnetic hydrogel prepared in Example 4 changes significantly under the action of magnetic fields of different frequencies. Under low-frequency conditions of approximately 1 Hz (… Figure 4 a) The resistance change ΔR / R0 exhibits periodic unidirectional oscillations, with a large oscillation peak of approximately 6-7% and a period of approximately 1 second (frequency approximately 1Hz). This large oscillation indicates that the low-frequency magnetic field allows the magnetic particles sufficient time to respond and form a stable conductive path, resulting in a significant reduction in resistance. At a high frequency of approximately 4Hz ( Figure 4 b) The small resistance variation and bidirectional oscillation (-2% to 5%) indicate that the high-frequency oscillation restricts the complete orientation of the particles, and the dynamic changes in the conductive path result in small resistance fluctuations.

[0141] The low-frequency response characteristics of the aforementioned liquid metal-based dual-network magnetic hydrogel can be used in biomedical sensors, while its rapid fluctuation characteristics in high-frequency response are suitable for electromagnetic shielding or high-frequency communication equipment. Optimizing particle concentration and matrix composition can further enhance its sensitivity and applicability. The resistance change of the liquid metal-based dual-network magnetic hydrogel under different frequency magnetic fields is the result of microstructure rearrangement and electromagnetic interactions. These characteristics not only reveal the complex physical mechanism of the dual-network magnetic hydrogel of this invention, but also lay a scientific foundation for its application in the fields of intelligent sensing and electromagnetic shielding.

[0142] In summary, this invention achieves superior EMI shielding performance through the synergistic effect of Fe3O4 nanoparticles and liquid metal microdroplets. The synergistic effect of liquid metal and Fe3O4 not only significantly enhances the mechanical properties of the dual-network composite hydrogel, but also innovatively reveals that the resistance of the dual-network magnetic hydrogel can change under varying magnetic fields. This lays a solid foundation for the application of the liquid metal-based dual-network magnetic hydrogel of this invention in magnetic devices, flexible multifunctional electromagnetic protection devices, and other fields.

[0143] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A liquid metal-based dual-network magnetic hydrogel, characterized in that, Including dual-network hydrogels and magnetic Fe3O4 nanoparticles loaded in the dual-network hydrogel network structure; The dual-network hydrogel includes a first network structure and a second network structure; wherein, the first network structure is a network structure formed by polymerizing sodium alginate chains coated with liquid metal, and the second network structure is a polyacrylamide network structure formed by polymerizing acrylamide monomers. The mass ratio of the liquid metal to the magnetic Fe3O4 nanoparticles is (0.5-2):(0.5-1).

2. The liquid metal-based dual-network magnetic hydrogel according to claim 1, characterized in that, The dual-network hydrogel has a porous sponge-like structure with a pore size of 20-50 μm. The sodium alginate coating of liquid metal forms micron-sized particles with a diameter of 1-3 μm; The magnetic Fe3O4 nanoparticles have a particle size of 50-200 nm.

3. The liquid metal-based dual-network magnetic hydrogel according to claim 1, characterized in that, The liquid metal is gallium, rubidium, cesium, or an alloy containing the above metals.

4. The liquid metal-based dual-network magnetic hydrogel according to claim 1, characterized in that, The liquid metal-based dual-network magnetic hydrogel has a tensile strength of 50–290 kPa, a Young's modulus of 60–250 kPa, and a toughness of 3.5–12 MJ / m. -3 .

5. A method for preparing the liquid metal-based dual-network magnetic hydrogel according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: S1. Preparation of liquid metal dispersion: Disperse liquid metal in water and use a cell disruptor for ultrasonic-assisted dispersion to obtain a micron-sized liquid metal dispersion; S2. Preparation of sodium alginate-coated liquid metal micron particles: The liquid metal aqueous dispersion obtained in S1 is added to the sodium alginate aqueous solution, and then dispersed again by ultrasonic-assisted dispersion using a cell disruptor to obtain a mixed solution containing sodium alginate-coated liquid metal micron particles. S3. Preparation of dual-network hydrogel precursor solution: Add acrylamide monomer, crosslinking agent and initiator to the mixed solution obtained in S2 to obtain dual-network hydrogel precursor solution; S4. Preparation of liquid metal-based dual-network magnetic hydrogel: Magnetic Fe3O4 nanoparticles are added to the dual-network hydrogel precursor solution obtained in S3 in a certain proportion and stirred evenly. The liquid metal-based dual-network magnetic hydrogel is obtained by UV-initiated cross-linking polymerization.

6. The method for preparing the liquid metal-based dual-network magnetic hydrogel according to claim 5, characterized in that, In steps S1 and S2, the cell disruptor is set to a power of 700-900W, a frequency of 30-50kHz, and an ultrasound time of 5-10min.

7. The method for preparing the liquid metal-based dual-network magnetic hydrogel according to claim 5, characterized in that, In step S2, the mass ratio of the liquid metal to sodium alginate is (0.5-2):0.2; The sodium alginate aqueous solution has a sodium alginate concentration of 0.03-0.05 g / mL.

8. The method for preparing the liquid metal-based dual-network magnetic hydrogel according to claim 5, characterized in that, In step S3, the mass ratio of sodium alginate, acrylamide monomer, crosslinking agent and initiator is 0.2:(1-3):(0.005-0.008):(0.01-0.02).

9. An application of the liquid metal-based dual-network magnetic hydrogel according to any one of claims 1-4, characterized in that, The liquid metal-based dual-network magnetic hydrogel, as a flexible multifunctional electromagnetic protection material, possesses both electromagnetic shielding performance and magnetic response modulation performance.

10. The application of the liquid metal-based dual-network magnetic hydrogel according to claim 9, characterized in that, The electromagnetic shielding mechanism of the liquid metal-based dual-network magnetic hydrogel is dominated by absorption loss. The liquid metal-based dual-network magnetic hydrogel exhibits periodic unidirectional oscillations in resistance change under a 1Hz magnetic field transformation, with a peak amplitude of 6-7%. The liquid metal-based dual-network magnetic hydrogel exhibits periodic bidirectional oscillations in resistance change under a 4Hz magnetic field, with a peak amplitude of -2% to 5%.

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